To improve radio signal quality, a technology has been developed that makes it possible to receive multiple radio waves having polarization planes different from each other by providing antennae for the respective polarization planes, and to prioritize a radio wave having higher strength to be used among the received radio waves. Such a technology is called polarization diversity.
An antenna that combines a dipole antenna and a slot antenna can be found, for example, in Patent Document 1.
This circular polarized antenna includes one antenna providing an antenna element extended in a predetermined direction, as well as another antenna that is configured as an aperture antenna to which a frame-shaped conductor is disposed.